NATATORES. CATARACTES. 513 



sessed by the former), are developed in their structure, par- 

 ticularly in the bill, feet, and tail, and as a marked differ- 

 ence also exists in their habits, it has been considered neces- 

 sary to establish a distinct genus for their reception. This 

 has been done by ILLIGER, in his Prodromus, under the ge- 

 neric name of Lestris, in which he has been followed by TEM- 

 MINCK, and several other writers; but as our countrymen ? 

 WILLOUGHBY and RAY, had previously separated them from 

 the genus Larus, under the appellation of Cataractes, I have 

 followed the rule so generally adopted by naturalists, that of 

 acceding to priority of imposition. In the cereous or soft 

 horny covering of the basal part of the bill, the acuminate 

 feathers of the neck, and their strong hooked talons, the 

 Skuas exhibit a distant affinity to birds of the raptorial or- 

 der, and their bold disposition and daring habits are also in 

 apparent accordance with this connexion. They are the de- 

 termined enemies of the Gulls, whom they unceasingly per- 

 secute on the wing, in order to make them disgorge their 

 half digested or recently swallowed food, and which is then 

 adroitly caught by the former before it can reach the water. 

 They also feed upon the flesh of the whale and other marine 

 animal substances. An approach to the Petrels is seen in their 

 general contour, and in the structure of their feet, the hind 

 toe in some species consisting of little more than a nail. 

 Their wings are long and pointed, and their flight, which is 

 strong, and at times astonishingly rapid, is performed by 

 successive jerks (in each of which a considerable curve is de- 

 scribed), bearing but little resemblance to that of the true 

 Gulls. They are natives of the Arctic Regions, and are found, 

 particularly during the season of reproduction, in very high 

 latitudes. The plumage of both sexes is alike, but some 

 species undergo great changes in their progress to maturity. 

 VOL. n. x k 



